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Example: Configuring an IS-IS Default Route Policy on Logical Systems

This example shows logical systems configured on a single physical router and explains how to configure a default route on one logical system.


No special configuration beyond device initialization is required before configuring this example.


This example shows a logical system redistributing a default route to other logical systems. All logical systems are running IS-IS. A common reason for a default route is to provide a path for sending traffic destined outside the IS-IS domain.

In this example, the default route is not used for forwarding traffic. The no-install statement prevents the route from being installed in the forwarding table of Logical System LS3. If you configure a route so it is not installed in the forwarding table, the route is still eligible to be exported from the routing table to other protocols. The discard statement silently drops packets without notice.


Figure 1 shows the sample network.

Figure 1: IS-IS with a Default Route to an ISPIS-IS with a Default Route to an ISP


CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode.


Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure an IS-IS default route policy on logical systems:

  1. Configure the logical tunnel interfaces.

  2. Enable IS-IS on the interfaces.

  3. Configure the default route on Logical System LS3.

  4. Configure the default route policy on Logical System LS3.

  5. Apply the export policy to IS-IS on Logical System LS3.

  6. If you are done configuring the device, commit the configuration.


From configuration mode, confirm your configuration by issuing the show logical-systems LS3 command. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.


Confirm that the configuration is working properly.

Verifying That the Static Route Is Redistributed


Make sure that the IS-IS policy is working by checking the routing tables.



The routing table on Logical System LS3 contains the default route from protocol Static. The routing tables on Logical System LS1 and Logical System LS2 contain the default route from protocol IS-IS. If Logical System LS1 and Logical System LS2 receive packets destined for networks not specified in their routing tables, those packets will be sent to Logical System LS3 for further processing. This configuration assumes that Logical System LS3 has a connection to an ISP or another external network.